Photographic elements generally form images through a reaction in which a developer reduces exposed silver halide to metallic silver. The oxidized developer then often reacts with a coupler that forms or releases an image-forming dye or other photographically useful groups; however, unwanted reactions between oxidized developer and components of the photographic element can cause adverse effects, such as dye stain. For example, in a multilayer color photographic element, a different color dye image is formed in each layer by the reaction of oxidized developer in that layer with a dye-forming coupler. Aerial oxidation of developer can cause reaction with dye-forming coupler where no silver development has taken place, leading to unwanted dye stain. Also, migration of oxidized developer from one layer to another can cause color contamination of one layer with image information from another layer, adversely effecting image reproduction.
In order to minimize unwanted reactions between oxidized developer and components of the photographic element, oxidized developer scavengers are used. These scavengers are incorporated in photographic elements in locations, such as interlayers, to prevent or reduce the reaction of oxidized developer with components in the element.
Hydroquinone derivatives have been widely used as oxidized developer scavengers. Such compounds are described, for example, in U.S. Pat. Nos. 2,728,659, 3,700,453, 3,982,944, and 4,366,236. They generally do not wander in the photographic element and provide effective scavenging of oxidized developer. The art teaches these scavengers may be incorporated in photographic elements as "oil in water dispersions". By this it is meant that the scavenger compounds are dissolved in a solvent, which is dispersed as fine droplets in an aqueous gelatin solution, and then coated as a layer of a photographic element.
While hydroquinone derivatives are generally effective as oxidized developer scavengers, they tend themselves to be oxidized by atmospheric oxygen. When photographic elements containing hydroquinone scavengers are stored for periods of time, the effectiveness of the scavenger can be reduced by aerial oxidation.